docs: def rotation_and_translation_from_matrix(matrix):
          """Helper to convert 4x4 matrix to rotation matrix and translation vector.
  
          Parameters
          ----------
          matrix : :obj:`numpy.ndarray` of float
              4x4 rigid transformation matrix to be converted.
  
          Returns
          -------
          :obj:`tuple` of :obj:`numpy.ndarray` of float
              A 3x3 rotation matrix and a 3-entry translation vector.
  
          Raises
          ------
          ValueError
              If the incoming matrix isn't a 4x4 ndarray.
          """
          if not isinstance(matrix, np.ndarray) or \
                  matrix.shape[0] != 4 or matrix.shape[1] != 4:
              raise ValueError('Matrix must be specified as a 4x4 ndarray')
          rotation = matrix[:3,:3]
          translation = matrix[:3,3]
          return rotation, translation